Multi-wall plastic sheets which are widely used for roofing or covering sides of buildings (outdoors) or rooms (indoors) are typically built of two or more plane walls separated by longitudinal ribs which define the space between the walls and define the internal structure. As seen in FIG. 1A, the ribs 11 of multi-wall sheet 10 may be formed vertically to the plane of the sheets (12) or in various angles other than right angle (14). Cross-section that is made vertically to the plane of the walls and to the direction of the ribs may reveal several patterns of sheets and ribs as seen in FIG. 1B, such as ribs that are parallel to each other (20B), ribs that are inclined in certain angle to each other (20A, 20C, 20D, 20E) ribs spaced apart from each other in different distances, etc. In common, the ribs define sub-spaces enclosed between two adjacent walls and two adjacent ribs (22A, 22B, 22C, etc.). These multi-wall sheets may be produced in various methods, such as extrusion.
Typically multi-wall sheets are produced as a ‘running’ sheet having width usually defined by the production ability of the producing machine, a length that is dictated by certain industrial/professional standard lengths that fit, for example, the sheets conveying means, the storing capabilities, customer's demands, etc. The multi-wall sheets have two ends, typically the narrow ends, which are perpendicular to the longitudinal direction of the ribs, open where the subspaces defined between adjacent walls and adjacent ribs are opened to the ambient at both ends of the respective multi-wall sheet as-produced.
Open ends of multi-wall sheets, as described above, cause undesired phenomena because these openings tend to enable penetration of dirt, insects, flies, rain, moisture, etc., into the sub-spaces. FIG. 2A depicts dirt, fungus and moss 200A created and/or accumulated at the end of a multi-wall sheet 200 due to accumulation of moisture and dirt that penetrated through the open end of multi-wall sheet 200. FIG. 2B depicts an insect or fly 200B trapped inside one sub-space of a multi-wall sheet 200 after having entered the subspace through an open end of multi-wall sheet 200. Even when measures known in the art are taken to seal the sheet's open ends according to known methods, these sealing means do not offer good enough solution. Such known methods include, for example, use of general-purpose adhesive tape, such as adhesive tape 302 of FIGS. 3A and 3B, adhered over sub-spaces 300B of multi-wall 300A, as seen in FIG. 3A and FIG. 3B.
Another method known in the art is pressing together the ends of a multi-wall sheet 400 along the edge at which sub-spaces end, so as to form a pressed-together end 402, as seen in FIGS. 4A, 4B, 4C and 4D. The performing of this press typically requires use of a special machine, involving applying high pressure and heat. This method may provide a good and durable sealing, but it may not be used on-site, for example for sealing an end formed after the sheet was cut-to a measure. Furthermore, sealing the ends of a multi-wall sheet this way changes the shape of the treated edge, thus interfering with commonly used auxiliary installation elements, such as frame profiles. Moreover, whenever a multi-wall is cut on-site of installation, for example, to fit to its location/role, along line that is perpendicular to the ribs, the sealing that was pre-made is lost and may not be resumed on site.
There is a need for a system and a method for sealing open ends of multi-wall sheets in a way that will provide high-quality, esthetic/elegant sealing that will not change the profile of the sheet at the sealed end, that will be durable during installation and in long usage terms and will be adapted to be carried outdoors at any site, away from the production line, where such multi-wall sheets are commonly used.